Less invasive test for Down syndrome

UK researchers have identified a test that can better pinpoint Down syndrome, and is much less invasive to expectant mothers.

Researchers have found a less invasive test that can be conducted during the first trimester of a woman’s pregnancy to see if a child has Down syndrome.

Kypros Nicolaides of King’s College London published findings in Ultrasound in Obstetrics & Gynecology discussing the new method that examines the infant’s DNA via the mother’s blood.

Currently, a woman can have a “combined test” between the 11th and 13th week of her pregnancy, which includes an ultrasound and blood test. The test is performed taking a woman’s age into account, and produces data about her chances that the child will have the syndrome.

Based on those results, a mother can choose to have one of two more invasive tests that can pinpoint the child’s condition. The chorionic villus sampling (CVS) analyzes a piece of the placenta, and an amniocentesis tests amniotic fluid from around the baby.

The new test uses fetal cell-free DNA (cfDNA) from a mother’s blood for Down syndrome and other chromosomal disorders. Scientists tested 1,005 pregnancies in 10 weeks and showed a lower false-positive rate and higher sensitivity than the combined test — in fact, the false-positive rate was 0.1 percent compared to 3.4 percent for the combined test.

“This study has shown that the main advantage of cfDNA testing, compared with the combined test, is the substantial reduction in false-positive rate,” the authors wrote. “Another major advantage of cfDNA testing is the reporting of results as very high or very low risk, which makes it easier for parents to decide in favor of or against invasive testing.”